In general, a steam turbine is a motor type in which thermal energy of steam is converted into a mechanical work. The steam turbine has less vibration, good efficiency, high speed and large horsepower and thus is widely used for thermal power generation or a main engine of a ship. In the steam turbine, high-temperature high-pressure steam generated in a boiler collides with a turbine wing that rotates high-speed steams of vapours that are spouted and expanded from nozzles or fixed wings, and a rotary shaft is rotated by an impulse action or a rebound action. Thus, the steam turbine is configured of nozzles that convert thermal energy of steam into speed energy and the turbine wing that converts speed energy into a mechanical work. The steam turbine includes an impulse type turbine that drives the turbine wing using only impulse force and a rebound type turbine or reaction-type turbine that drives the turbine wing using rebound force.
Korean Patent Registration No. 10-1052253 (published on Apr. 15, 2009) discloses a reaction-type turbine. In the reaction-type turbine, unlike a conventional turbine, a working fluid is jetted from jet rotation portions to the outside, and a turbine shaft is rotated by repulsive force thereof. In the reaction-type turbine, pressure of an inlet side of a housing is high, and pressure of an outlet side of the housing is relatively low. Thus, axial direction force is applied in a direction from the inlet side to the outlet side such that a thrust bearing supporting an axial load of a rotary shaft may be easily damaged.